The dollar fell on Wednesday as optimism about a potential coronavirus vaccine was offset by worries about how and when the drug will be delivered and by a surge of new infections in Europe and the United States.

The yen scraped back some losses against the U.S. dollar on Tuesday, after the safe currency slumped on news of the development of a coronavirus vaccine which raised optimism of a global economic recovery.

The dollar hit a 10-week low on Monday as investors heralded Joe Biden’s election as U.S. president by buying trade-exposed currencies on expectations that a calmer White House could boost world commerce and that monetary policy will remain easy.

The dollar steadied against many currencies on Friday, after much slides earlier. Though, more losses are likely as a contentious U.S. presidential election diminished hopes for large stimulus to support the economy any time soon.

The dollar slipped as Democrat Joe Biden edged ever so closer to the White House, while Republicans look likely to retain control of the Senate and expected to hamper Biden’s fiscal policy agenda.

The U.S. dollar jumped and risk-sensitive currencies weakened on Wednesday as early results in the U.S. presidential election showed a very tight race, as Democratic challenger Joe Biden leading the race.

The U.S. dollar hovered just below a one-month high on Tuesday, as investors opted for caution in the hours ahead of polls opening on election day in the United States, while the Australian dollar slipped after a central bank rate cut.

Traders are bracing for more volatility in currency markets as the virus spreads in Europe, Britain, and the United States, fanning concerns that economic growth will weaken once again. The dollar fell against the yen, higher against the euro.

The dollar clung to small gains on Tuesday as the dollar's safe-haven appeal was strengthened by worries about a second wave of COVID-19, which drove the steepest stock market selloff in a month and underpinned a bond rally.

The dollar found support on Monday, as surging coronavirus cases in Europe and the U.S. and a lack of progress toward a U.S. stimulus package put traders in a cautious mood. Hopes for a Brexit trade deal held sterling steady.

The dollar inched higher at the end of a tough week on Friday, having shed almost a cent against the euro and suffered its largest weekly drop against the yen in a month, as a measured U.S. presidential debate left investors in a cautionary mood.

The U.S. dollar treaded water against most major currencies on Thursday as U.S. stimulus talks remain as the focus for markets with trading buffeted over recent days by the extent of progress made on the potential size of the stimulus aid package.